Motor vehicle courtesy/reading lights are provided in the interior of motor vehicles in order to supply interior lighting so that the occupants of the motor vehicle can read, consult maps, look for objects, and perform other functions which would be difficult to perform with little or no interior light. A common problem encountered when utilizing courtesy/reading lights is that they illuminate the entire interior of the vehicle and do not control the amount of light each occupant of the vehicle receives. This can be especially dangerous because the light emitted from conventional courtesy/reading lights is often too bright and, therefore, interferes with a driver's ability to safely operate the motor vehicle. There have been several attempts to reduce the light and glare from courtesy/reading lights on the driver while providing enough light for the rest of the occupants.
One conventional means for controlling the amount of light in the interior of a motor vehicle is by installing a courtesy/reading light which is capable of being turned so as to be aimed in a certain direction or area of the motor vehicle. This type of aimed courtesy/reading light often produces a very bright, concentrated ray which i generally too bright in some areas and not bright enough in others. Consequently, the light must be regularly adjusted depending on the function it is being used for. If the light is being continually operated over a period of time the area around it often becomes too hot to touch and hence adjust. This particular light also has a tendency to reflect off certain interior surfaces, such as the dash board, into the line of vision of the driver. Additionally, because the aimed courtesy/reading light comprises multiple parts, some of which are moveable, it is more likely to be subject to mechanical failure than a courtesy/reading light comprising few, nonmoveable parts. The aimed courtesy/reading light also exhibits a greater tendency to rattle, an undesirable quality in the motor vehicle environment where noise levels are traditionally kept to a minimum. An additional drawback of the aimed courtesy/reading light is that it typically costs more to manufacture and install than other courtesy/reading lights which do not require complex assembly techniques and multiple, moveable parts.
Another means presently utilized for controlling the amount of light inside the motor vehicle is by tinting, frosting, or stippling the lens that covers the courtesy/reading light. Typically such treated lenses are able to reduce the glare on the driver, but they also significantly decrease the light in the rest of the motor vehicle. Often the glare on the driver is not sufficiently diminished to allow the motor vehicle to be safely operated with the courtesy/reading light on, of the occupants are not provided with enough light to see by. These lenses do not selectively control the distribution of light in different areas of the interior of the motor vehicle, but instead simply decrease the amount of light in the entire interior. Other attempts to uniformly treat or cover the courtesy/reading light lens have encountered the same difficulty.
Alternatively, although not presently employed as a means for controlling light in motor vehicles, some fluorescent lights utilize an exterior clear plastic cover which is covered with a pattern of dark lines that intersect to act as a dimmer for the fluorescent light. The pattern of dark lines intersect more in some areas of the plastic cover than others, hence the amount of light which passes through these areas is less. By turning the cover to an area with a dense amount of lines the light is dimmed over the entire area. Once again, although this pattern is capable of reducing the glare from a light by dimming the light as it passes through the pattern of intersecting lines, it does this uniformly and does not selectively shade certain areas and not others. Therefore, because this type of light dimming device would not selectively control the amount of light the individual occupants of the motor vehicle receive, it would not be an appropriate solution.
Another possible means to selectively control the distribution of light in the interior of a motor vehicle would be by utilizing a light control film. Light control film comprises extremely narrow, dark or opaque parallel lines printed on a thin, stiff plastic sheet for controlling light distribution in the same manner that venetian blinds control light as it passes through them. By printing the lines so that they are angled at different degrees the light becomes slanted in a certain direction as it passes through the openings between the lines of the light control film. Although acceptable for some applications light control film is not well suited for a motor vehicle environment.
Four very important features of any interior component of a motor vehicle are design flexibility, durability, cost and aesthetic appeal. Light control film is lacking in all of these areas. Design flexibility is important to motor vehicle manufacturers because different models of motor vehicles often require interior components of different size, shape, and color. If an interior component is capable of being easily adapted for a variety of motor vehicles at a minimum cost it is frequently the component of choice. The direction and degree to which the lines on the light control film are angled are predetermined by the manufacturer of the film, therefore, selection of lines at particular angles is limited. Additionally, because the light control film is manufactured on stiff plastic sheet it is not capable of being formed onto a multiple contoured surface. Since the light control film must be purchased from a supplier and then molded to the courtesy/reading light lens it does not allow for design flexibility and is therefore, not well suited for use in a motor vehicle environment.
Because motor vehicles can be on the road for up to 10 years or more, durability is another important feature to consider when choosing a motor vehicle component. Any item which can be easily scratched or nicked is not usually used in or on a motor vehicle. Currently available light control film has a polished surface which is very susceptible to scratching and would, therefore, under normal wear become scratched and nicked, losing its luster and any aesthetic appeal it originally had. Aesthetic appeal is a very important aspect of a motor vehicle's interior because many people spend up to 15 hours per week or more inside of their motor vehicles. Also, aside from being unappealing to look at, a scratched or nicked component may take away from the motor vehicle's resale value. Additionally, because of its susceptibility to scratching the light control film would have to be carefully stored and handled adding additional cost to the product.
Due to the competitive nature of the automotive market cost control is always an important consideration. Currently available light control film is relatively expensive to purchase and because the film is costly to store and handle it is too expensive to be used in most motor vehicle applications, especially as a cover for a courtesy/reading light. For the foregoing reasons light control film is not an acceptable solution to the aforementioned problem of shading the driver of a motor vehicle while proving the passengers with enough light to see by.
Finally, some motor vehicle's utilize multiple courtesy/reading lights in order to direct light to certain areas of the motor vehicle's interior. Although utilizing multiple courtesy/reading lights does enable certain areas of the motor vehicle's interior to receive more light than others, such multiple lights still illuminate the entire interior of the motor vehicle and like other conventional courtesy/reading lights tend to reflect off of certain interior surfaces, such as the dashboard. Therefore, multiple courtesy/reading lights do not control light inside of the motor vehicle well enough to be operated without interfering with the driver's ability to safely operate the motor vehicle.